Quick answer. Bronchiolitis is a common viral infection of the small airways in the lungs that mainly affects babies under one year, often caused by RSV, leading to wheeze, fast breathing and feeding difficulty. Most cases are mild, but if a baby is breathing very fast or with great effort, has blue lips, is feeding poorly or seems dehydrated, seek urgent care or call 995.
Bronchiolitis is one of the most common chest infections in babies, and a frequent reason for infant hospital admissions worldwide, including in Singapore. It is caused by viruses that inflame the smallest airways in the lungs, the bronchioles, making them swollen and clogged with mucus so that breathing becomes harder and faster. The respiratory syncytial virus (RSV) is the usual culprit. Most babies recover well with supportive care at home, but a minority, especially the very young or those born early, can become unwell quickly.
This guide explains what bronchiolitis is, the symptoms in babies, why it happens, how it is assessed and how it is treated. It also makes clear the breathing warning signs that mean a baby needs to be seen urgently. Because young infants can tire and deteriorate faster than older children, close watching of feeding and breathing is the most important part of home care.
At a glance
| Stage | What you might see | What to do |
|---|---|---|
| Mild | Runny nose, cough, mild wheeze, feeding well | Home care; watch feeding and breathing |
| Moderate | Faster breathing, eating less than usual | See a doctor the same day |
| Concerning | Hard, fast breathing, few wet nappies | Seek urgent medical care |
| Emergency | Struggling to breathe, blue lips, very drowsy | Call 995 now |
| Recovering | Cough lingering but breathing easy, feeding back to normal | Continue home care; cough can last weeks |
What is bronchiolitis?
Bronchiolitis is a viral infection that inflames the bronchioles, the tiny air passages deep in the lungs. The lining swells and produces mucus, narrowing the airways so a baby has to work harder to breathe and may wheeze. It typically starts like a cold and then moves to the chest over a few days.
It mostly affects babies in the first year of life, and is most common and most severe in the youngest infants. In Singapore, as elsewhere, RSV is the leading cause. Most babies have a mild illness that peaks around day three to five and improves over one to two weeks, although the cough can linger longer.
Symptoms & signs
Bronchiolitis usually begins with cold-like symptoms before the chest becomes involved. Watch for:
- A runny or blocked nose and a cough, often the first signs
- Wheeze, a whistling sound on breathing out
- Faster breathing than usual
- Feeding less, taking shorter feeds or tiring during feeds
- A mild fever
- Fewer wet nappies than normal, a sign of reduced feeding or dehydration
In babies, breathing and feeding are the key things to track. A baby who is breathing comfortably and feeding reasonably well is usually managing, while difficulty with either is a reason to seek help.
Causes & risk factors
Bronchiolitis is caused by viruses spread through droplets and contaminated hands and surfaces. The main factors are:
- RSV and other viruses: respiratory syncytial virus is the commonest cause, with several other respiratory viruses also responsible.
- Young age: babies under one year, and particularly those under six months, are most at risk.
- Prematurity: babies born early have smaller, more vulnerable airways.
- Underlying conditions: heart or lung conditions, or a weakened immune system, increase risk of severe illness.
- Exposure: older siblings, childcare and tobacco smoke in the home raise the chance and severity.
How bronchiolitis is diagnosed
Bronchiolitis is usually diagnosed by examination, based on the baby’s age, the typical pattern of a cold moving to the chest, and the findings the doctor hears when listening to the lungs. Tests are often not needed. A doctor will:
- Assess breathing rate and effort, oxygen levels, alertness and hydration
- Listen to the chest for wheeze and crackles
- Check how feeding is going and the number of wet nappies
- Occasionally take a nasal swab to identify the virus, or arrange a chest X-ray, mainly in more severe or unclear cases
The main job of assessment is to judge how hard the baby is breathing and whether they are still feeding and hydrated.
Treatment options
There is no specific cure for bronchiolitis, and because it is viral, antibiotics do not help. Care is supportive and aims to keep the baby comfortable, fed and breathing safely:
- Feeding and fluids: offer smaller, more frequent feeds; the priority is keeping the baby hydrated.
- Nasal care: gently clearing a blocked nose with saline drops can help feeding and breathing.
- Fever relief: paracetamol may be used for fever or discomfort following dosing advice.
- Hospital care: babies who are feeding poorly, dehydrated or needing help with breathing may be admitted for oxygen, feeding support or fluids and monitoring.
Inhalers, steroids and antibiotics are generally not effective for typical bronchiolitis. Prevention focuses on hand hygiene, avoiding smoke exposure and, where appropriate, RSV protection, which a doctor can advise on.
When to see a doctor & which specialist
Call 995 or go to the nearest A&E immediately if a baby:
- Is breathing very fast or with great effort, with the chest or ribs pulling in
- Has long pauses in breathing, or grunts with each breath
- Has blue or grey lips, tongue or face
- Is very drowsy, floppy, or difficult to wake
Seek same-day medical review if the baby is feeding much less than usual, has had far fewer wet nappies, has a high fever, or you are worried about their breathing. For non-urgent assessment a GP is a good first stop; for ongoing or complex breathing concerns, care may involve a respiratory specialist, who you can find through the best respiratory physicians in Singapore directory. Bronchiolitis affects the small airways in the lungs and is different from croup, which swells the upper airway and causes a barking cough, and from asthma, which is uncommon as a diagnosis in this young age group.
Related guides
- Best Respiratory & Lung Clinics in Singapore — our editorial shortlist
- Sarcoma
- Croup
- Stomach cancer
- Pancreatic cancer
- Peptic ulcer
Sources
- NHS – Bronchiolitis
- Mayo Clinic – Bronchiolitis
- KK Women's and Children's Hospital
- HealthHub Singapore – Child health
- MOH Singapore
Part of our Children’s health guides · Browse all health topics